In an earlier post I detailed how arm dynamics should be ballet slow, whereas your legs need to be dynamic and fast. There's a tad more to a well-rounded and enthralling program than that though. To stay interesting and not appear to be frozen in a mood, to show that you have moxie and can relate to your program's music, both arm and leg dynamics need to vary across time. Not randomly though, but rather softly and thematically matched to the changes in your music's tempo or intonation.
When the music is bold and sweeping your arms can be more directive and your leg movements can be longer, more rhythmic strokes. If your music is soft and gentle, your arms can by lyrical and your legs and feet can move to a more eclectic pattern. When the music is staccato your footwork should be precise and demonstrative, but your arms should be ballet (we are watching your footwork, don't distract us with your arms).
Getting into the flow of the music without being imprisoned by it is a gentile art all its own. Your motion and dynamic changes should coincide with the timepoints where your music's theme changes, but you don't have to match a stroke to every downbeat, or accent an arm movement on every bar.